Heavy oil and bitumen resources are supplementing the decline in the production of conventional light and medium crude oil, and production form these resources is expected to dramatically increase. Pipeline expansion is expected to handle the increase in heavy oil production, however, the heavy oil must be treated in order to permit its transport by pipeline. Presently heavy oil and bitumen crudes are either made transportable by the addition of diluents or they are upgraded to synthetic crude. However, diluted crudes or upgraded synthetic crudes are significantly different from conventional crude oils. As a result, bitumen blends or synthetic crudes are not easily processed in conventional fluid catalytic cracking refineries. Therefore, in either case the refiner must be configured to handle either diluted or upgraded feedstocks.
Many heavy hydrocarbon feedstocks are also characterized as comprising significant amounts of BS&W (bottom sediment and water). Such feedstocks are not suitable for transportable by pipeline, or upgrading due to the sand, water and corrosive properties of the feedstock. Typically, feedstocks characterized as having less than 0.5 wt. % BS&W are transportable by pipeline, and those comprising greater amount of BS&W require some degree of processing and treatment to reduce the BS&W content prior to transport. Such processing may include storage to let the water and particulates settle, followed by heat treatment to drive of water and other components. However, these manipulations are expensive and time consuming. There is therefore a need within the art for an efficient method for upgrading feedstock comprising a significant BS&W content prior to transport or further processing of the feedstock.
Heavy oils and bitumens can be upgraded using a range of rapid processes including thermal (e.g., U.S. Pat. Nos. 4,490,234; 4,294,686; 4,161,442), hydrocracking (U.S. Pat. No. 4,252,634) visbreaking (U.S. Pat. Nos. 4,427,539; 4,569,753; 5,413,702) or catalytic cracking (U.S. Pat. Nos. 5,723,040; 5,662,868; 5,296,131; 4,985,136; 4,772,378; 4,668,378, 4,578,183) procedures. Several of these processes, such as visbreaking or catalytic cracking, utilize either inert or catalytic particulate contact materials within upflow or downflow reactors. Catalytic contact materials are for the most part zeolite based (see for example U.S. Pat. Nos. 5,723,040; 5,662,868; 5,296,131; 4,985,136; 4,772,378; 4,668,378, 4,578,183; 4,435,272; 4,263,128), while visbreaking is typically utilizes inert contact material (e.g., U.S. Pat. Nos. 4,427,539; 4,569,753), carbonaceous solids (e.g., U.S. Pat. No. 5,413,702), or inert kaolin solids (e.g., U.S. Pat. No. 4,569,753).
The use of fluid catalytic cracking (FCC), or other, units for the direct processing of bitumen feedstocks is known in the art. However, many compounds present within the crude feedstocks interfere with these processes by depositing on the contact material itself These feedstock contaminants include metals such as vanadium and nickel, coke precursors such as Conradson carbon and asphaltenes, and sulfur, and the deposit of these materials results in the requirement for extensive regeneration of the contact material. This is especially true for contact material employed with FCC processes as efficient cracking and proper. temperature control of the process requires contact materials comprising little or no combustible deposit materials or metals that interfere with the catalytic process.
To reduce contamination of the catalytic material within catalytic cracking units, pretreatment of the feedstock via visbreaking (U.S. Pat. Nos. 5,413,702; 4,569,753; 4,427,539), thermal (U.S. Pat. Nos. 4,252,634; 4,161,442) or other processes, typically using FCC-like reactors, operating at temperatures below that required for cracking the feedstock (e.g, U.S. Pat. Nos. 4,980,045; 4,818,373 and 4,263,128;) have been suggested. These systems operate in series with FCC units and function as pre-treaters for FCC. These pretreatment processes are designed to remove contaminant materials from the feedstock, and operate under conditions that mitigate any cracking. This ensures that any upgrading and controlled cracking of the feedstock takes place within the FCC reactor under optimal conditions.
Several of these processes (e.g., U.S. Pat. Nos. 4,818,373; 4,427,539; 4,311,580; 4,232,514; 4,263,128;) have been specifically adapted to process “resids” (i.e., feedstocks produced from the fractional distillation of a whole crude oil) and bottom fractions, in order to optimize recovery from the initial feedstock supply. The disclosed processes for the recovery of resids, or bottom fractions, are physical and involve selective vaporization or fractional distillation of the feedstock with minimal or no chemical change of the feedstock.
These processes are also combined with metals removal and provide feedstocks suitable for FCC processing. The selective vaporization of the resid takes place under non-cracking conditions, without any reduction in the viscosity of the feedstock components, and ensures that cracking occurs within an FCC reactor under controlled conditions. None of these approaches disclose the upgrading of feedstock within this pretreatment (i.e., metals and coke removal) process. Other processes for the thermal treatment of feedstocks involve hydrogen addition (hydrotreating), which results in some chemical change in the feedstock.
U.S. Pat. No. 4,294,686 discloses a steam distillation process in the presence of hydrogen for the pretreatment of feedstock for FCC processing. This document also indicates that this process may also be used to reduce the viscosity of the feedstock such that the feedstock may be suitable for transport within a pipeline. However, the use of short residence time reactors to produce a transportable feedstock is not disclosed.
There is a need within the art for a rapid and effective upgrading process of a heavy oil or bitumen feedstock that involves a partial chemical upgrade or mild cracking of the feedstock in order to obtain a product characterized in having a reduced viscosity over the starting material. Ideally this process would be able to accommodate feedstocks comprising significant amounts of BS&W. This product would be transportable for further processing and upgrading. Such a process would not involve any catalytic-cracking activity due to the known contamination of catalyst contact materials with components present in heavy oil or bitumen s feedstocks. The rapid and effective upgrading process would produce a product characterized in having reduced viscosity, reduced metal content, increased API, and an optimal product yield.
The present invention is directed to the upgrading of heavy hydrocarbon feedstocks, for example but not limited to heavy oil or bitumen feedstocks, that utilizes a short residence pyrolytic reactor operating under conditions that cracks and chemically upgrades the feedstock. The feedstock used within this process may comprise significant levels of BS&W and still be effectively processed, thereby increasing the efficiency of feedstock handling. The process of the present invention provides for the preparation of a partially upgraded feedstock exhibiting reduced viscosity and increased API gravity. The process described herein selectively removes metals, salts, water and nitrogen from the feedstock, while at the same time maximizes the liquid yield, and minimizing coke and gas production. Furthermore, this process reduces the viscosity of the feedstock to an extent which can permit pipeline transport of the feedstock without addition of diluents. The partially upgraded product optionally permits transport of the feedstock offsite, to locations better equipped to handle refining. Such facilities are typically located at a distance from the point where the crude feedstock is obtained.